JP2007129583A - Multiple-optical-axis photoelectric sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multiple-optical-axis photoelectric sensor capable of determining that ambient light is emitted by the same type of multiple-optical-axis photoelectric sensor, and also, capable of preventing occurrence of malfunctions due to the light emitted by the same type of multiple-optical-axis photoelectric sensor. <P>SOLUTION: The multiple-optical-axis photoelectric sensor is provided with an ambient-light detection means which detects the presence of the ambient light for each optical axis L on the basis of detection of a light-receiving signal, in at least either of a inspection period immediately before t5 a light-emission period of a light-projecting element, and that of immediately after the light-emission period of the light-projecting element regarding the light-receiving element constituting the optical axis L while being paired with the light-projecting element; an ambient-light type determination means which executes light-reception retry operation for allowing the light-receiving element in an optical axis L2 with detected ambient light to receive light again, without executing light emission of the light-projecting element in an optical axis L3 subsequent to the light emission of the light-projecting element in the optical axis L2 with detected ambient light, when the ambient light (a1) is detected by the ambient-light detection means, and also, determines types of ambient light on the basis of whether or not a light-receiving signal of the light-receiving element constituting the optical axis with detected ambient light is detected in the inspection period when executing the light-reception retry operation; and a cycle adjusting means for changing the next scan cycle when the light-receiving signal is detected by the ambient-light type determination means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a multi-optical axis photoelectric sensor.

  For example, a multi-optical axis photoelectric sensor that detects that an object has entered a detection area is known. The multi-optical axis photoelectric sensor includes a projector having a plurality of light projecting elements, and a light receiver having a plurality of light receiving elements arranged so as to constitute an optical axis so as to face the plurality of light projecting elements, respectively. ing. This multi-optical axis photoelectric sensor repeats the light projecting / receiving operation in which the light receiving elements sequentially emit light at a predetermined light projecting period and receive light by the light receiving elements, and based on the light reception signal of the light receiving elements. Thus, the light shielding of each optical axis is detected, and an intruding object into the detection area is detected.

  A plurality of multi-optical axis photoelectric sensors may be arranged close to each other in order to detect that an object has entered in a wider area. As described above, when a plurality of multi-optical axis sensors are arranged, there is a concern that the light emitted by the same type of multi-optical axis photoelectric sensors arranged close to each other enters the light receiving element and malfunctions.

  Moreover, there are various types of disturbance light in addition to the light emitted by the same type of multi-optical axis photoelectric sensor. For example, this disturbance light has a continuous influence on the detection of an intruding object such as lighting in a factory, or is a periodic light such as a temporary light generated during welding work or a warning light. In some cases, the light is incident on only a part of the light receiving elements of the multi-optical axis photoelectric sensor. In addition, the disturbance light includes light that enters the light receiving element from an unspecified direction, such as light emitted from a rotating light of a transport vehicle that circulates in the factory. Therefore, it is necessary to prevent such disturbance light from entering the light receiving element and malfunctioning, and Patent Documents 1 and 2 are known as techniques for that purpose.

  In the multi-optical axis photoelectric sensor described in Patent Document 1, the presence / absence of disturbance light is determined within one predetermined period immediately before and immediately after the light emission period of each light projecting element, and it is determined that disturbance light has been detected. In this case, the retry operation for projecting and receiving again the optical axis in which the disturbance light is detected is repeatedly performed up to a preset number of retries possible. This multi-optical axis photoelectric sensor performs the light projecting / receiving operation of the next optical axis when it is determined that the disturbance light is not detected based on the light reception level of the light reception signal at the time of the retry operation. Accordingly, it is determined that the object is not in the detection area, and malfunction is prevented.

Further, in the multi-optical axis photoelectric sensor described in Patent Document 2, when disturbance light exceeding a predetermined number of times is detected within a period nearest to the light projecting period of each light projecting element, the cycle of the light projecting / receiving operation is set. The disturbance light emission period and the light projecting / receiving operation period are prevented from matching, and the disturbance light prevents the object from being erroneously determined to be out of the detection area.
JP 2003-347916 A JP-A-2005-114551

  However, in the multi-optical axis photoelectric sensor described in Patent Document 1, even when the disturbance light temporarily generated is detected immediately before the light projecting operation of the light projecting element having a single optical axis, etc. Since the disturbance light temporarily generated during the retry operation is not detected, the influence of the disturbance light can be eliminated and the light projecting and receiving operations after the next optical axis can be performed sequentially. For disturbance light periodically generated like light emitted by the photoelectric sensor, the same type of multi-optical axis photoelectric sensor is again used immediately before the light projecting operation of the light projecting element during the next light projecting / receiving operation. There is a problem that the light emitted from the camera must be detected and a retry operation must be performed. In particular, in the optical axis where disturbance light is repeatedly detected, the light projecting element repeats light projection by repeating the retry operation, and this light projecting element becomes a light projecting element constituting another optical axis. There is a problem that it is significantly deteriorated.

  Furthermore, in the multi-optical axis photoelectric sensor described in Patent Document 2, depending on the situation in which the same type of multi-optical axis photoelectric sensor is disposed in proximity, the light emitted by the same type of multi-optical axis photoelectric sensor is a single light. In the case where the light emitted by this same type of multi-optical axis photoelectric sensor is not detected on the other optical axis, it may be detected more than a predetermined number of times within the immediate period of the light projecting period of the light projecting element of the optical axis. Even in such a case, it is determined that light emitted by the same type of multi-optical axis photoelectric sensor will be detected within the most recent period of the light projecting period of the light projecting elements of all the optical axes, and the cycle of the light projecting / receiving operation is determined. Will change.

  The present invention has been proposed in view of such a situation, and it is determined that disturbance light is light emitted by the same type of multi-optical axis photoelectric sensor, and the same type of multi-optical axis photoelectric sensor is provided. An object of the present invention is to provide a multi-optical axis photoelectric sensor that can prevent malfunction due to emitted light.

  The invention of claim 1 is a projector having a plurality of light projecting elements, and a light projecting control means for repeating a light projecting scan operation of sequentially emitting the plurality of light projecting elements at a predetermined light projecting period at a predetermined scan period, A light receiver having a plurality of light receiving elements arranged so as to constitute an optical axis facing the plurality of light projecting elements, respectively, and when any one of the plurality of light projecting elements emits light, The light receiving element constituting the optical axis and detecting a light reception signal from the light receiving element to detect light blocking of the optical axis, and any one of the plurality of light projecting elements When the light emitting element emits light, light reception from the light receiving element is performed in the inspection period immediately before and immediately after the light emitting period of the light projecting element with respect to the light receiving element that forms a pair with the optical axis. Check the signal Disturbance light detecting means for detecting the presence or absence of disturbance light for each optical axis based on, and the optical axis on which the disturbance light is detected on condition that the disturbance light is detected by the disturbance light detection means The light projecting element on the next optical axis does not emit light, and the light receiving element facing the light projecting element does not receive light, and the light receiving element on the optical axis where the disturbance light is detected receives light again. The type of disturbance light is determined based on whether or not a light reception signal is detected for the light receiving element constituting the optical axis in which the disturbance light is detected in the inspection period during the light reception retry operation. When the received light signal is detected by the disturbance light type determination means for determining and the disturbance light type determination means, the next scan cycle is changed and the light reception signal is determined by the disturbance light type determination means. Signal is a multi-optical axis photoelectric sensor and a cycle adjusting unit which does not change the next time of the scan cycle if not detected.

  According to a second aspect of the present invention, in the first aspect, the disturbance light type determination unit performs at least the first light reception when performing the light reception retry operation on the optical axis where the disturbance light is detected by the disturbance light detection unit. In the retry operation, the light projecting element does not emit light on the optical axis where the disturbance light is detected, and the light receiving element facing the light projecting element performs a light receiving operation.

  According to a third aspect of the present invention, in the first or second aspect, the disturbance light detecting means detects a light reception signal from the light receiving element in a period immediately before and immediately after a light emission period of the light projecting element. The presence or absence of disturbing light is detected for each optical axis based on the above, and the disturbing light detecting means detects the disturbing light in the period immediately before the light emitting period of the light projecting element and the disturbing light detecting means In the case where light is detected in a period immediately after the light emission period of the light projecting element, the period adjusting unit is a multi-optical axis photoelectric sensor that changes the scan period to a different period.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, when the disturbance light detection unit detects the disturbance light immediately before the light emission period of the light projecting element, the period adjustment unit includes: When the disturbance light detection means detects the disturbance light immediately after the light emission period of the light projecting element, the period adjustment means is a multi-optical axis photoelectric sensor that lengthens the scan period. is there.

  A fifth aspect of the present invention is the multi-optical axis photoelectric sensor according to any one of the first to fourth aspects, further comprising a light receiving retry operation limiting means for performing the light receiving retry operation up to a predetermined number of retryable times.

  A sixth aspect of the present invention is the multi-optical axis photoelectric sensor according to the fifth aspect, wherein the number of retries is a total number of retry operations for all optical axes.

  According to a seventh aspect of the present invention, the disturbance light determining means according to any one of the first to sixth aspects, wherein the number of times of the light receiving retry operation reaches the retry possible number of times and the last light receiving retry operation is performed. When the disturbance light is detected, the multi-optical axis photoelectric sensor is provided with an abnormality detection signal output means for outputting an abnormality detection signal notifying that the disturbance light is detected in an abnormal state.

<Invention of Claim 1>
According to the present invention, disturbance light is detected without the light emitting element emitting light on the optical axis next to the optical axis where disturbance light is detected, and the light receiving element facing the light projecting element does not receive light. Whether or not a light receiving signal is detected for the light receiving element that constitutes the optical axis in which disturbance light is detected during the inspection period during the light receiving retry operation. Based on the received light signal detected at the time of the light receiving retry operation, the light (for example, the same type of light) Whether or not the light emitted from the optical axis photoelectric sensor is detected can be determined.
In addition, when the received light signal is detected by the disturbance light type determination unit, the cycle adjustment unit changes the next scan cycle, so that the changed scan cycle can be changed to, for example, the scan cycle of a multi-optical axis photoelectric sensor of the same model. The light receiving time of the light receiving element and the light emitting time of light emitted by the same type of multi-optical axis photoelectric sensor do not match, and there are intruding objects in the detection area, It is possible to prevent light from being emitted by the same type of multi-optical axis photoelectric sensors arranged in close proximity and determining that there is no object in the detection area, thereby preventing malfunction.

<Invention of Claim 2>
According to the invention of claim 2, when the disturbance light type determination means performs the light reception retry operation on the optical axis in which the disturbance light is detected by the disturbance light detection means, the disturbance light is at least in the first light reception retry operation. Since the light receiving element facing the light projecting element does not emit light at the detected optical axis, the light receiving element facing the light projecting element performs the light receiving operation, so the light receiving element of the optical axis where the disturbance light is detected faces the light receiving element. The light emitted by the light projecting element can be received without receiving the light emitted from the light projecting element. Based on the light reception signal caused by the disturbance light, the disturbance light is emitted at a predetermined light projection period (for example, the same type). It is possible to determine whether or not the light is emitted from the multi-optical axis photoelectric sensor.
In addition, when performing the light receiving retry operation, since the light projecting element of the optical axis where the disturbance light is detected is not emitted at least in the first light receiving retry operation, the disturbance light is not used as in the conventional multi-optical axis photoelectric sensor. The light projecting element of the optical axis in which the light is detected does not repeat reprojection, and the deterioration of the light projecting element can be suppressed from proceeding remarkably.

<Invention of Claims 3 and 4>
According to the invention of claim 3, when the disturbance light detecting means detects disturbance light in a period immediately before the light emitting period of the light projecting element, and when the disturbance light detecting means detects disturbance light in a period immediately after the light emitting period of the light projecting element. The period adjusting means preferably changes the scanning period to a different period. In particular, as in the invention of claim 4, the disturbance light detecting means detects the disturbance light immediately before the light emitting period of the light projecting element. If the period adjusting means shortens the scanning cycle when detected in, the light emitting point of each light projecting element is moved in the direction opposite to the direction in which the ambient light approaches the light emitting point of each light projecting element. Therefore, it is possible to avoid that the shortened scan cycle matches the scan cycle of the same type of multi-optical axis photoelectric sensor.
On the other hand, when the disturbance light detecting means detects the disturbance light immediately after the light emitting period of the light projecting element, the period adjusting means lengthens the scan period. The optical element can be moved in a direction opposite to the direction of approaching the light emitting point of the optical element, and the widened scanning period can be prevented from matching the scanning period of the same type of multi-optical axis photoelectric sensor.

<Invention of Claim 5>
According to the fifth aspect of the present invention, since the light receiving retry operation limiting means for performing the light receiving retry operation as a limit of the predetermined number of retries is provided, in the plurality of light receiving retry operations, the type of disturbance light is, for example, a fluorescent lamp, It is possible to determine whether the light emitted from the warning light or the light emitted from the same type of multi-optical axis photoelectric sensor, and to increase the probability of detecting the light emitted from the same type of multi-optical axis photoelectric sensor.

<Invention of Claim 6>
According to the sixth aspect of the present invention, since the number of retries is the total number of retries for all the optical axes, the light receiving retries are continuously performed even for the optical axis in which disturbance light is concentrated and detected. Compared with the case where the number of retries is determined for each optical axis, the light receiving retry operation for all the optical axes can be efficiently performed according to the detection state of disturbance light.

<Invention of Claim 7>
According to the seventh aspect of the present invention, in the case where disturbance light is detected by the disturbance light determination means when the number of light reception retry operations reaches the number of possible retry operations and the last light reception retry operation is performed, disturbance light is detected. Since there is an abnormality detection signal output means for outputting an abnormality detection signal for informing that the abnormal state is detected, the multi-optical axis photoelectric device is informed that there is a possibility that the light shielding determination operation cannot be performed due to an abnormal state. It is possible to prompt the inspection of the sensor.

<Embodiment 1>
Embodiment 1 of the present invention will be described with reference to FIGS. 1 to 6. In the multi-optical axis photoelectric sensor 1 of the present embodiment, as shown in FIG. 1, the projector 10 is disposed to face the light receiver 30 with a predetermined detection area interposed therebetween. For example, ten projector elements T (T1 to T10, for example, light emitting diodes) are arranged in a row in the projector 10.

  As shown in the drawing, ten light receiving elements J (J1 to J10, for example, photodiodes) facing each of the ten light projecting elements T are arranged in the light receiver 30. Note that the letter N used in the following description indicates an arbitrary order (1 to 10) of the optical axis L (L1 to L10) illustrated. The arbitrary order of the optical axis L corresponds to the counter value of the shift registers 13 and 35 described later.

  Each light projecting element T is connected to a driving circuit 11, and this driving circuit 11 is connected to a light projecting CPU 14 via an AND circuit 12 and a light projecting side shift register 13. The light emitting side CPU 14 receives the synchronization signal D output from the light receiving side CPU 34 provided in the light receiver 30, transmits the light projecting signal E (see FIG. 1) to the AND circuit 12, and projects the drive circuit control signal. To the side shift register 13.

  The light projection signal E is a signal for causing each light projecting element T to project at a predetermined period U (see FIG. 3). The drive circuit control signal is a signal for determining the light projection timing of each light projecting element T. When receiving the drive circuit control signal, the light emitting side shift register 13 transmits a selection signal to each AND circuit 12 in correspondence with the value of the counter.

  Each AND circuit 12 outputs a signal to each drive circuit 11 when it receives the light projection signal E and the selection signal. Each drive circuit 11 supplies a drive current to each light projecting element T when receiving a signal from each AND circuit 12. Each light projecting element T emits light when supplied with a drive current. The multi-optical axis photoelectric sensor 1 repeatedly performs a light projection scanning operation of sequentially projecting ten light projecting elements T1 to T10 with a predetermined period U according to a light projection signal E, a drive circuit control signal, and a selection signal. . In the present embodiment, as described above, the light projecting scan operation is performed by the drive circuit 11, the AND circuit 12, the light projecting side shift register 13, the light projecting side CPU 14, and the light receiving side CPU 34. Accordingly, the drive circuit 11, the AND circuit 12, the light projecting side shift register 13, the light projecting side CPU 14, and the light receiving side CPU 34 constitute the light projecting control means of the present invention.

  Each light receiving element J is connected to a light receiving amplifier 31 and also connected to an A / D converter 33 via each switch element 32. The light receiving side CPU 34 receives a signal output from the A / D converter 33 and detects whether or not light is received based on this signal.

  The light-receiving side CPU 34 uses a program stored in a memory (not shown) to detect the light-shielding detection timing at which the cycle and phase coincide with the light-projecting signal E for each light-projecting element T. Is slightly advanced in disturbance light detection timing (first disturbance light detection period t5, which will be described later, inspection period), and disturbance light detection timing (second disturbance light detection period t8 in which the phase is slightly delayed from this light shielding detection timing signal). A gate control signal for turning on each switch element 32 over a period of time including the inspection period) is transmitted to the light receiving side shift register 35. The light receiving side shift register 35 sequentially transmits selection signals to the respective switch elements 32 in the same manner as the light projecting side shift register 13. As a result, the light reception signal from each light receiving element J is transmitted to the light receiving side CPU 34 via the A / D converter 33.

  The light receiving side CPU 34 determines whether or not the light projecting elements T perform the light projecting operation at the light shielding detection timing, and the light reception signal (the amount of received light) transmitted from the A / D converter 33 exceeds the object detection threshold. To determine whether to block the light. This light shielding determination is performed using the light receiving amplifier 31, the switch element 32, the A / D converter 33, the light receiving side CPU 34, and the light receiving side shift register 35. Accordingly, the light receiving amplifier 31, the switch element 32, the A / D converter 33, the light receiving side CPU 34, and the light receiving side shift register 35 constitute a light shielding determination unit of the present invention.

  In the light receiving side CPU 34, at the disturbance light detection timing, each light projecting element T does not perform the light projecting operation, and the light reception signal (the amount of received light) transmitted from the A / D converter 33 is the disturbance light detection threshold value. The presence or absence of ambient light is detected by determining whether or not the above has been exceeded. The disturbance light detecting means for detecting the presence or absence of the disturbance light includes a light receiving amplifier 31, a switch element 32, an A / D converter 33, a light receiving side CPU 34, and a light receiving side shift register 35.

  When the light receiving side CPU 34 determines that disturbance light has been detected in each optical axis L, it transmits a disturbance light detection signal G to the light projection side CPU 14. When receiving the disturbance light detection signal G, the light emitting side CPU 14 transmits a counter lock signal to the light emitting side shift register 13 to prevent the counter value from being increased. Thereafter, the light receiving side CPU 34 receives the gate control signal from the light receiving side over the light blocking detection timing and the disturbance light detecting timing after the period U has elapsed since the light projecting element T of the optical axis L that detected the disturbance light is projected. Transmit to the shift register 35. The shift register 35 transmits a selection signal to the switch element 32 connected to the optical axis (here, the optical axis where disturbance light is detected) corresponding to the value of the counter. Thereby, the light receiving element J of the optical axis in which the disturbance light is detected performs a light receiving retry operation, and the light receiving signal from the light receiving element J is transmitted to the light receiving side CPU 34 via the A / D converter 33. Based on this light reception signal, the light receiving side CPU 34 determines whether or not the disturbance light is light emitted from the same type of multi-optical axis photoelectric sensor. As described above, this light receiving retry operation is performed using the light receiving amplifier 31, the switch element 32, the A / D converter 33, the light receiving side CPU 34, and the light receiving side shift register 35. Therefore, the light receiving amplifier 31, the switch element 32, the A / D converter 33, the light receiving side CPU 34, and the light receiving side shift register 35 correspond to the disturbance light type determining means of the present invention. Thereafter, the light receiving side CPU 34 transmits the synchronization signal D to the light projecting side CPU 14, and the light projecting side CPU 14 transmits the light projecting signal E to the AND circuit 12. At this time, the light projection signal E is transmitted to the AND circuit 12 connected to the optical axis L that has detected the disturbance light by the selection signal transmitted by the light projection side shift register 13, and the optical axis L from which the disturbance light has been detected. The light projecting element T is projected.

  When the light receiving side CPU 34 detects disturbance light on any one of the optical axes L, the light receiving side CPU 34 changes the scan cycle T according to a program stored in a memory (not shown), and sends the synchronization signal D to the light emitting side. The timing to transmit to the CPU 14 is changed. The light receiving side CPU 34 corresponds to the period adjusting means of the present invention.

  Next, the control method of the multi-optical axis photoelectric sensor 1 of this embodiment is demonstrated. The light emitting side CPU 14 executes each process shown in FIG. When the power of the multi-optical axis photoelectric sensor 1 is turned on, the light emitting side CPU 14 sets the value N of the counter of the light emitting side shift register 13 to “1” (S1). When the value N of this counter is set to “1”, the light-projecting side shift register 13 transmits a selection signal to the AND circuit 12 connected to the light projecting element T1 via the drive circuit 11.

  After S1, it waits for the light emitting side CPU 14 to receive the synchronization signal D transmitted by the light receiving side CPU 34, and it is determined whether or not this synchronization signal D has been received (S2). When it is determined that the synchronization signal D has been received in S2, the light projection side CPU 14 performs a light projection signal output process for outputting the light projection signal E (see FIG. 1) to the AND circuit 12 (S3). The AND circuit 12 that has received the selection signal and the projection signal E by the projection signal output process (S3) and the projection element T1 connected to the drive circuit 11 are illustrated in FIG. In addition, the light projecting operation of the first optical axis L1 is performed.

  After the light projection signal output process (S3), it is determined whether or not the disturbance light detection signal G transmitted by the receiving CPU 34 is received (S4). When it is determined in S4 that the disturbance light detection signal G (see FIG. 1) is not received (no disturbance light is detected), the light emitting side CPU 14 adds 1 to the counter value N of the light emitting side shift register 13. Then, the value N of this counter is set to “2” (S5), and then it is determined whether or not the value N of this counter exceeds 10 (S6).

  In S6, when it is determined that the counter value N does not exceed 10 (here, the counter value N is 2), the light-projecting side shift register 13 projects the selection signal via the drive circuit 11. The data is transmitted to the AND circuit 12 connected to the element T2, and enters a standby state. Thereafter, it is determined whether or not the synchronization signal D has been received (S2). When this synchronization signal D is received, the light projecting element T2 is shown in FIG. 3B by the light projection signal output process (S3). As shown in FIG. 4, the light projecting operation of the second optical axis L2 is performed.

  Further, in S4, it is determined whether or not the disturbance light detection signal G is received, and when it is determined that the disturbance light detection signal G is not received, the light emitting side CPU 14 determines the value of the counter of the light emitting side shift register 13 1 is added to N, and the value N of this counter is set to “3” (S5). As a result, the light projecting element T3 performs the light projecting signal output processing (S3) as shown in FIG. The light projecting operation of the third optical axis L3 is performed. As described above, when the light projection side CPU 14 determines that the disturbance light detection signal G is not received, the light projecting elements T1 to T10 have the light projecting elements as can be understood from FIGS. In synchronization with the output timing of the signal E, the light projecting operation is performed once in order, and the light projecting scan operation for one cycle (scan cycle T15) is completed.

  If it is determined in S4 that the ambient light detection signal G has been received, a light projection operation standby process (S7) is performed. In the light projection operation standby process (S7), the light projection side CPU 14 performs control so as not to transmit the light projection signal E by a program stored in the memory. The light projection CPU 14 determines whether or not the light projection signal output process (S3) is controlled so as not to transmit the light projection signal E, and is controlled so as not to transmit the light projection signal E. When it is determined, the light projection signal E is not output to the AND circuit 12.

  On the other hand, the light receiving side CPU 34 executes each process shown in FIGS. When the power of the multi-optical axis photoelectric sensor 1 is turned on, the light receiving side CPU 34 determines whether or not the standby time t2 has elapsed (S9). In this S9, as shown in FIGS. 3A and 3J, whether or not the time (waiting time t2) until the light-emission scanning operation of the next cycle is started has elapsed. Determine whether.

  In S9, when it is determined that the standby time t2 has elapsed, scan cycle initialization processing (S10) is performed. In this scan cycle initialization process (S10), the light receiving side CPU 34 sets the scan cycle to T15.

  After the scan cycle initialization process (S10), the light receiving side CPU 34 sets the value N of the counter of the light receiving side shift register 35 to “1” (S11). When the value N of this counter is set to “1”, the light receiving side shift register 35 transmits the selection signal S1 (see FIG. 1) to the switch element 32 connected to the light receiving element J1 via the light receiving amplifier 31. . As a result, the switch element 32 is turned on, and the light receiving signal of the light receiving element J1 (first optical axis L1) is transmitted to the A / D converter 33, as can be understood from FIGS. 1 and 3A. .

  In S11, the retry count K (re-projection count) is further set to “0”, and then a standby state is entered. After S11, the light receiving side CPU 34 determines whether or not a predetermined light receiving timing has been reached (S12), and when it is determined that the light receiving side CPU 34 has reached the light receiving timing, reading of the light receiving signal at the first non-light emitting time is read. Processing (S13) is performed. In the first non-light-projecting received light signal reading process (S13), the light receiving side CPU 34 reads the received light signal transmitted by the A / D converter 33 into a memory (not shown). The magnitude of the received light reception signal is the amount of light received by the light receiving element J1 before the light projecting element T1 starts the light projecting operation (first disturbance light detection period t5 in FIG. 6A) (when light is not projected). (Light reception level).

  An object detection process (S14) is performed after the light reception signal reading process (S13) during the first non-light projection. In this object detection process (S14), the light receiving side CPU 34 transmits the synchronization signal D to the light projecting side CPU 14. In this case, the light projecting element T1 performs the light projecting operation as illustrated in FIG. 3A by the light projecting signal output process (S3) of FIG. Further, in the object detection process (S14), the light receiving side CPU 34 receives a light receiving signal (see FIG. 3A) transmitted by the A / D converter 33 in synchronization with the light projecting operation of the light projecting element T1. Read into memory (not shown). The magnitude of the received light reception signal is the amount of light received by the light receiving element J1 when the light projecting element T1 starts the light projecting operation (light reception level during light projection). In the object detection process (S14), the light reception level at the time of projection read into the memory is compared with a predetermined object detection threshold. The light-receiving side CPU 34 determines that the object is not detected in the detection area when the light reception level at the time of light projection exceeds the object detection threshold value, and the light reception level at the time of light projection is below the object detection threshold value. If it is determined that the object has been detected in the detection area.

  After the object detection process (S14), it is determined whether disturbance light has been detected (S15). In S15, the light receiving side CPU 34 compares the non-light emitting light reception level read into the memory by the first non-light emitting light reception signal reading process (S13) with a predetermined disturbance light detection threshold value, and the light is not emitted. When the received light level exceeds the disturbance light detection threshold, it is determined that disturbance light has been detected.

  In S15, when the light receiving side CPU 34 determines that ambient light is not detected, 1 is added to the value N of the counter of the light receiving side shift register 35, and the value N of this counter is set to “2” (S16). Subsequently, it is determined whether or not the value N of the counter exceeds 10 (S17).

  If it is determined in S17 that the counter value N does not exceed 10 (here, the counter value N is 2), as can be understood from FIGS. For L10, it is determined whether or not the above-described light reception timing has been reached (S12), the first non-light-projecting received light signal reading process (S13), the object detection process (S14), and whether or not ambient light has been detected. (S15), a process of adding 1 to the counter value N of the light receiving side shift register 35 (S16) is performed. Thus, when it is determined that ambient light is not detected, the light receiving operation is performed once in order in synchronization with the output timing of the synchronizing signal D, as can be understood from FIGS. This completes the light receiving operation for one cycle.

  When detecting the disturbance light in S15, the light receiving side CPU 34 performs the following processing as shown in the flowchart of FIG. Here, disturbance light will be described by taking, as an example, light emitted by a multi-optical axis photoelectric sensor of the same type as the multi-optical axis photoelectric sensor 1 of the present embodiment, as illustrated in FIG. As shown in the figure, the disturbance light is generated by a light projection scanning operation with a scanning period of T15.

  In S15, the light-receiving side CPU 34 emits disturbance light immediately before the light projecting operation of the light projecting element T2 (second optical axis L2) as illustrated in FIGS. 6 (a1), (b), and (B). When it is determined that detection has been performed in one disturbance light detection period t5), the number of retries (re-light reception) K set in S22, which will be described later, is the number of retries possible for all optical axes L1 to L10 (here, 9 times) It is determined whether or not it exceeds (S18).

  In S18, when the light receiving side CPU 34 determines that the number of retries K does not exceed the possible number of times, whether or not the light receiving side CPU 34 has detected disturbance light within the first disturbance light determination period t5. It is judged (S19). In S19, the light receiving side CPU 34 compares the non-light emitting light reception level read into the memory by the first non-light emitting light reception signal reading process (S13) with a predetermined disturbance light detection threshold, When it is determined that the hourly light reception level has exceeded the disturbance light detection threshold, it is determined that the disturbance light has been detected immediately before the light projection operation of the light projecting element T1 (first disturbance light determination period t5).

  If it is determined in S19 that disturbance light has been detected immediately before the light projection operation of the light projecting element T1 (first disturbance light determination period t5), a retry (re-light reception) process (S20) is performed. In this retry (re-light reception) process (S20), the light receiving side CPU 34 transmits the disturbance light detection signal G to the light projecting side CPU 14, and the light projecting elements T2 and T3 stop light projection (light projection stop). The detection time of the light receiving signal of the light receiving element J2 within the period t6 (see FIG. 6B) is read into a memory (not shown). The light projection stop period t6 is the same time (disturbance light discrimination time) as the time during which each light receiving element J performs the light receiving operation.

  After S20, the light receiving side CPU 34 has detected a light receiving signal in the retry (re-light receiving) process (S20), and a predetermined time has elapsed since the disturbance light was detected in the first disturbance light detection period t5. It is determined whether it is time (S21). Here, as shown in FIG. 6B, when the first disturbance light determination period t7 has elapsed since the disturbance light was detected, it is determined whether the disturbance light has been detected again. As can be understood from FIGS. 6A1 and 6A, the first disturbance light determination period t7 is set to the same period as the light projection interval U (light projection period) of each light projecting element T.

  In S21, when the light-receiving side CPU 34 determines that the disturbance light has been detected again when the first disturbance light determination period t7 has elapsed, as can be understood from FIGS. 6A1, 6A, and 6B. Then, it is determined that the disturbance light is light emitted from the same type of multi-optical axis photoelectric sensor, and the first scan cycle changing process (S25) is performed. In the first scan cycle changing process (S25), as can be understood from FIGS. 3A and 6A, the scan cycle is changed from T15 to T15 without changing the projection interval U between the optical axes. Change to -α. The relationship between the scan periods is T15> T15-α. This α can be determined by changing to an appropriate value. In S19, when it is determined that disturbance light is not detected immediately before the light projecting operation of the light projecting element T1, the processes of S16 and S17 are performed.

  After the first scan cycle changing process (S25), 1 is added to the value of the retry counter of the light receiving side CPU 34 (S22), and then the reprojection / light receiving process (S23) is performed. In the re-projection / light-receiving process (S23), the light-receiving side CPU 34 transmits the synchronization signal D to the light-projecting side CPU 14. As a result, as shown in FIG. 6B, the light projecting element T2 (second optical axis L2 from which the disturbance light is detected) performs the light projecting operation again. Further, in the re-projection / light-receiving process (S23), as can be understood from FIG. 6B, the light-receiving side CPU 34 performs the light projection by the light projecting element T2 in synchronization with the light projecting operation of the light projecting element T2. The amount of light received by the light receiving element J2 at the start is read into the memory.

  After this re-projection / light-receiving process (S23), a re-light-receiving object detection process (S24) is performed. In the re-light-receiving object detection process (S24), the light-receiving side CPU 34 compares the amount of light received by the light receiving element J2 read into the memory by the re-projection / light-receiving process (S23) with a predetermined object detection threshold. In the re-light-receiving object detection process (S24), the same process as the object detection process (S14) described above is performed.

  After the re-light-receiving object detection process (S24), the light-receiving side CPU 34 performs the processes of S16 and S17 described above. In S21, when the light receiving side CPU 34 determines that the disturbance light is not detected when the first disturbance light determination period t7 has elapsed, the disturbance light is not light emitted by the same type of multi-optical axis photoelectric sensor. The first scan cycle changing process (S25) described above is not performed, and the above-described processes (S22 to S24) are performed.

  In S18, when the light receiving side CPU 34 determines that the number of retries K exceeds the possible number (here, 9 times), an abnormality detection signal output process (S26) is performed. In the abnormality detection signal output process (S26), an abnormality detection signal is transmitted to, for example, an operation device for the operation indicator lamp, and the operation indicator is turned on by driving the actuator device. The multi-optical axis photoelectric sensor of this embodiment notifies that the number of retries has exceeded the possible number of times by turning on the operation indicator lamp.

  In the multi-optical axis photoelectric sensor 1 of the present embodiment, the light-receiving side CPU 34 transmits disturbance light immediately before the light projecting operation of the light projecting element T2 (second optical axis L2) (first disturbance light detection) by S19 in FIG. When it is determined that the detection has occurred in the period t5), the first disturbance light determination is performed after detecting the disturbance light based on the detection time of the received light signal in the retry (re-light reception) processing (S20) in S21 in FIG. When the period t7 (the light projection interval U) has elapsed, it is determined again whether ambient light has been detected. In this way, the first disturbance light determination period t7 is set to the same period as the light projection interval U of the light projecting elements included in the same type of multi-optical axis photoelectric sensor, and the light projection of the light projecting elements T2 and T3 is stopped. In this state, if the light receiving side CPU 34 determines again whether or not ambient light has been detected in S21, the light emitted from the same type of multi-optical axis sensor that the light receiving side CPU 34 projects at the light projecting interval U is emitted. It can be determined whether or not is detected. In this multi-optical axis photoelectric sensor, during the retry (re-light reception) process (S20), the light projecting element T2 of the second optical axis L2 in which the disturbance light is detected stops the light projection, and the light is projected by S21. Based on the detection time of the light reception signal of the light receiving element J2 within the period during which the optical element T2 stops projecting light (projection halt period t6, see FIG. 6B), the disturbance light has the same type of multi-optical axis. Whether or not the light emitted from the photoelectric sensor is judged. For this reason, the light receiving element J2 can receive disturbance light without receiving the light emitted by the light projecting element T2, and the disturbance light has the same type of disturbance light based on the light reception signal of the light receiving element J2 caused by the disturbance light. It can be determined whether or not the light is emitted from the optical axis photoelectric sensor. In addition, unlike the conventional multi-optical axis photoelectric sensor, the light projecting element T2 of the second optical axis L2 in which the disturbance light is detected stops the light projection in the retry (re-light receiving) process (S20). In addition, the light projecting element having the optical axis in which the disturbance light is detected does not repeat light projection, and the deterioration of the light projecting element can be suppressed from proceeding remarkably.

  Further, in this multi-optical axis photoelectric sensor 1, when the light receiving side CPU 34 determines that the light emitted from the same type of multi-optical axis sensor is detected in S21, the first scan cycle changing process (S25). The scan period is changed from T15 to T15-α. For this reason, in this multi-optical axis photoelectric sensor 1, the changed scanning cycle (T15-α) can be made different from the scanning cycle (T15) of the same type of multi-optical axis photoelectric sensor. It is possible to prevent the light emitted from the optical axis photoelectric sensor from being detected immediately before the light projecting operation of the light projecting element T2 (second optical axis L2). Therefore, in this multi-optical axis photoelectric sensor 1, the light receiving element J2 receives the light emitted from the same type of multi-optical axis photoelectric sensor even if there is an object in the detection area, and the object detection process (S14). Therefore, it can be prevented that the object is not detected in the detection area. In this multi-optical axis photoelectric sensor 1, since the scan cycle (T15-α) is kept different from the scan cycle (T15) of the same type of multi-optical axis photoelectric sensor, it is understood from FIG. As can be done, the scan cycle is changed from T15-α to T15 by the scan cycle initialization process (S10), and the projection scan operation is performed.

  In the multi-optical axis photoelectric sensor 1 of the present embodiment, when the light receiving side CPU 34 determines that the number of retryable times (here, 9 times) has not been exceeded by S18 in FIG. By the process (S20), the light receiving element J2 (second optical axis L2 from which the disturbance light is detected) performs the light receiving operation again. Therefore, in the light receiving retry operation (S18 to S20 in FIG. 5) a plurality of times (here, 9 times), the type of disturbance light is, for example, light emitted from a fluorescent lamp or a warning lamp, or the same type of multi-optical axis photoelectrics. It is possible to determine whether the light is emitted from the sensor and to increase the probability of detecting the light emitted from the same type of multi-optical axis photoelectric sensor. In addition, in this multi-optical axis photoelectric sensor 1, for example, disturbance light is concentrated and detected immediately before the light projection operation of the light projecting element T2 (second optical axis L2) (first disturbance light detection period t5). Even if there is a case, the light receiving retry operation of the light receiving element J2 can be continuously performed within the range not exceeding the retry possible number by S18 to S20 in FIG. 5, and the disturbance light is detected in the light receiving retry operation. Can be efficiently performed with respect to the optical axis.

  In the multi-optical axis photoelectric sensor 1 of the present embodiment, the light receiving side CPU 34 determines that disturbance light has been detected in S15 in FIG. 4, and the number of retries K is the number of retries (here, S18 in FIG. 5). 9 times), the abnormality detection signal is transmitted to, for example, the operation device of the operation indicator lamp by the abnormality detection signal output process (S26), and the operation indicator lamp is driven by driving the actuator device. Control to light up. Therefore, in this multi-optical axis photoelectric sensor 1, by turning on the operation indicator lamp, there is a possibility that disturbance light may be continuously detected and an intruding object may not be detected, or an apparatus failure may occur, so that the light receiving side The CPU 34 determines that the number of retries has been exceeded and informs that there is a possibility that the intruding object cannot be detected, and can prompt the inspection of the multi-optical axis photoelectric sensor 1.

  In the multi-optical axis photoelectric sensor 1 of the present embodiment, unlike the conventional multi-optical axis photoelectric sensor, the disturbance light detection period (here, the first disturbance light detection period t5) is generally employed. It is not necessary to make it longer than the ambient light detection period, and the scan cycle including the ambient light detection period becomes longer, and it is possible to avoid delaying the response time for light shielding determination in each optical axis.

<Embodiment 2>
A second embodiment of the present invention will be described with reference to FIGS. 1, 2, and 7 to 10. FIG. Here, the same configurations and control methods as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. In the multi-optical axis photoelectric sensor 1A of the present embodiment, it is determined whether or not disturbance light is detected immediately before and after the light projecting operation of each of the light projecting elements T1 to T10. As described above, the light-projecting CPU 14 executes each process shown in FIG.

  On the other hand, the light receiving side CPU 34 executes each process shown in FIGS. The flowchart shown in FIG. 7 differs from the flowchart shown in FIG. 4 (Embodiment 1) in the second non-projection received light signal reading process (S13A). In the second non-light-projecting received light signal reading process (S13A), the light-receiving side CPU 34 immediately after the light projecting operation of each light projecting element T (for example, the second disturbance light detection period t8 in FIG. 10B). The amount of light received by each light receiving element J facing each light projecting element T (the light receiving level during non-light projection) is read into a memory (not shown).

  In S15 in FIG. 7, the light-receiving side CPU 34 detects disturbance light in which the light-receiving level at the time of non-light-projection read into the memory by the first and second light-projection signals at the time of non-light-projection (S13, S13A) is determined in advance. If it is determined that the light reception level during non-projection exceeds the disturbance light detection threshold value as compared with the threshold value, it is determined that disturbance light has been detected. In S15, for example, when it is determined that disturbance light is detected on the second optical axis L2, the light receiving side CPU 34 determines whether or not the retry count K exceeds the number of retries possible (S18). If it is determined that the number K of times does not exceed the possible number of times, it is determined in S19 whether or not ambient light has been detected within the first ambient light determination period t5.

  In S19, when it is determined that the disturbance light is detected within the first disturbance light determination period t5, and the light receiving side CPU 34 determines that the disturbance light is detected immediately before the light projecting operation of the light projecting element T2, a retry ( Re-light reception) processing (S20A) is performed. In this retry (re-light reception) process (S20A), the light receiving side CPU 34 transmits a disturbance light detection signal G to the light projecting side CPU 14, and the light projecting elements T2 and T3 stop light projection (light projection stop). The detection time of the light reception signal of the light receiving element J2 within the period t9 (see FIG. 9B) is read into a memory (not shown). The light projection stop period t9 is the same time (disturbance light discrimination time) as the time during which each light receiving element J performs the light receiving operation.

  After the retry (re-light reception) process (S20A), based on the detection time of the light reception signal in the retry (re-light reception) process (S20A), the first disturbance light determination period t7 (FIG. 9B) ) See)), it is determined again whether ambient light has been detected (S21A).

  In S21A, the light receiving side CPU 34 detects the disturbance light again when the first disturbance light determination period t7 has elapsed, and immediately before the light projecting operation of the light projecting element T2 emits the light emitted by the same type of multi-optical axis photoelectric sensor. When it is determined that detection is to be performed, the above-described first scan cycle changing process (S25) and the above-described processes (S22 to S24) are performed, and as illustrated in FIG. Change to T15-α. In S21A, when it is determined that the disturbance light is not detected when the first disturbance light determination period t7 has elapsed, it is determined that the disturbance light is not the light emitted by the same type of multi-optical axis photoelectric sensor. The above-described processes (S22 to S24) are performed without performing the scan cycle changing process (S25).

  On the other hand, when the light receiving side CPU 34 determines in S19 that the disturbance light is not detected within the first disturbance light determination period t5, the disturbance light detection determination process (S27) is performed. In this disturbance light detection determination process (S27), the disturbance light is detected within the second disturbance light detection period t8, and it is determined that the disturbance light is detected immediately after the light projecting operation of the light projecting element T2. After the disturbance light detection determination process (S27), a retry (re-light reception) process (S20B) is performed. In this retry (re-light reception) process (S20B), the light receiving side CPU 34 transmits a disturbance light detection signal G to the light projecting side CPU 14, and the light projecting elements T2 and T3 stop light projection (light projection stop). The detection time of the light receiving signal of the light receiving element J2 within the period t9 (see FIG. 10B) is read into a memory (not shown).

  After the retry (re-light reception) process (S20B), based on the detection time of the received light signal in the retry (re-light reception) process (S20B), the disturbance light is detected and then the second disturbance light determination period t11 (FIG. 10B ) See)), it is determined again whether ambient light has been detected (S28). The second disturbance light determination period t11 is set to the same period as the light projection interval U of each light projecting element T.

  In S28, the light receiving side CPU 34 detects disturbance light again when the second disturbance light determination period t11 has elapsed, and immediately after the light projecting operation of the light projecting element T2 emits light emitted by the same type of multi-optical axis photoelectric sensor. When it is determined that detection is to be performed, second scan cycle change processing (S30) is performed. In the second scan cycle changing process (S30), as can be understood from FIG. 10A, the scan cycle is changed from T15 to T15 + α without changing the projection interval U between the optical axes. The relationship between the scan periods is T15 + α> T15> T15−α. In S28, when it is determined that the disturbance light is not detected when the second disturbance light determination period t11 has elapsed, it is determined that the disturbance light is not the light emitted by the same type of multi-optical axis photoelectric sensor, and the second The above-described processes (S22 to S24) are performed without performing the scan cycle changing process (S30).

  In the multi-optical axis photoelectric sensor 1A of the present embodiment, the receiving side CPU 34 transmits disturbance light to the light projecting element T2 as can be understood from FIGS. 9A, 9B, and 9B by S19 in FIG. When it is determined that detection is performed immediately before the light projecting operation of (second optical axis L2) (first disturbance light detection period t5), the light reception in the retry (re-light reception) processing (S20A) is performed in S21 in FIG. Based on the signal detection time, when the first disturbance light determination period t7 (the light projection interval U) has elapsed since the disturbance light was detected, it is determined whether the disturbance light has been detected again. In the multi-optical axis photoelectric sensor 1A, when the light-receiving side CPU 34 detects disturbance light again in S21 and determines that the disturbance light is light emitted by the same type of multi-optical axis sensor, The scan cycle is changed from T15 to T15-α by the scan cycle change process (S25). For this reason, in this multi-optical axis photoelectric sensor 1A, the changed scan cycle (T15-α) can be made different from the scan cycle (T15) of the same type of multi-optical axis photoelectric sensor. It is possible to prevent the light emitted from the optical axis photoelectric sensor from being detected immediately before the light projecting operation of the light projecting element T2 (second optical axis L2). Therefore, in this multi-optical axis photoelectric sensor 1A, even though there is an object in the detection area, the light receiving element J2 receives the light emitted from the same type of multi-optical axis photoelectric sensor, and the object detection process (S14). Therefore, it can be prevented that the object is not detected in the detection area.

  On the other hand, in this multi-optical axis photoelectric sensor 1A, as shown in FIGS. 10 (a1), 10 (b) and 10 (B), the receiving side CPU 34 can understand the disturbance by the disturbance light detection determination process (S27) in FIG. When it is determined that light is detected immediately after the light projecting operation of the light projecting element T2 (second optical axis L2) (second disturbance light determination period t8), a retry (re-light reception) process is performed in S28 in FIG. Based on the detection time of the received light signal in (S20B), whether or not the disturbance light is detected again when the second disturbance light determination period t11 (the light projection interval U) has elapsed since the disturbance light was detected. to decide. In the multi-optical axis photoelectric sensor 1A, when the light-receiving side CPU 34 detects disturbance light again in S28 and determines that the disturbance light is light emitted by the same type of multi-optical axis sensor, The scan cycle is changed from T15 to T15 + α by the scan cycle change process (S30). For this reason, in this multi-optical axis photoelectric sensor 1A, the changed scanning cycle (T15 + α) can be made different from the scanning cycle (T15) of the same type of multi-optical axis photoelectric sensor. It is possible to prevent the light emitted from the photoelectric sensor from being detected immediately after the light projecting operation of the light projecting element T2 (second optical axis L2). Therefore, in this multi-optical axis photoelectric sensor 1A, as in the case where the light emitted by the same type of multi-optical axis photoelectric sensor is detected immediately before the light projecting operation of the light projecting element T2 (second optical axis L2), By the object detection process (S14), it can be determined that an object is not detected in the detection area.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention. In the following description, the same components as those in the first embodiment and the second embodiment described above are denoted by the same reference numerals, and the description thereof is omitted.
(1) In the first and second embodiments described above, for example, disturbance light is detected immediately before the light projecting operation of each of the light projecting elements T1 to T10 or just before and immediately after each of the light projecting elements T1 to T10. However, as shown in FIGS. 11A1 and 11B, for example, immediately after the light projecting operation of the second optical axis L2 (the second disturbance light detection period) When it is determined that the detection is made at t8), the scan cycle may be changed from T15 to T15 + α as shown in FIG. As a result, the changed scan cycle (T15 + α) can be made different from the scan cycle (T15) of the same type of multi-optical axis photoelectric sensor, and the light receiving element J2 emits the light emitted by the same type of multi-optical axis photoelectric sensor. It can prevent receiving light and determining that an object is not detected within a detection area.
(2) In the first and second embodiments described above, 1 is added to the value of the retry counter of the light receiving side CPU 34 every time the retry (re-light reception) process is performed, but this retry is performed every time the re-projection light reception process is performed. You may make it add 1 to the value of a counter.

Electrical configuration diagram of multi-optical axis photoelectric sensor according to Embodiments 1 and 2 of the present invention 6 is a flowchart showing control of a light-projecting side CPU of a multi-optical axis photoelectric sensor according to Embodiments 1 and 2. Timing chart of multi-optical axis photoelectric sensor according to Embodiment 1 First flowchart showing control of light receiving side CPU The second flowchart Timing chart when disturbance light is detected immediately before the light projecting operation on the second optical axis First flowchart showing the control of the light receiving side CPU of the multi-optical axis photoelectric sensor according to the second embodiment. The second flowchart Timing chart when disturbance light is detected immediately before the light projecting operation on the second optical axis Timing chart when disturbance light is detected immediately after the light projecting operation on the second optical axis Timing chart of multi-optical axis photoelectric sensor according to another embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1A ... Multi-optical axis photoelectric sensor 10 ... Light projector 11 ... Drive circuit (light projection control means)
12 ... AND circuit (light projection control means)
13 ... Projection side shift register (projection control means)
14 ... Projection side CPU (projection control means)
30... Light receiver 31... Light receiving amplifier (light shielding determination means, disturbance light detection means, disturbance light type determination means)
32 ... Switch element (light-shielding determination means, disturbance light detection means, disturbance light type determination means)
33... A / D converter (light shielding determination means, disturbance light detection means, disturbance light type determination means)
34. Light receiving side CPU (light projection control means, light shielding determination means, disturbance light detection means, disturbance light type determination means, period adjustment means)
35: Light-receiving side shift register (light-shielding determination means, disturbance light detection means, disturbance light type determination means)
J1 to J10 ... light receiving elements L1 to L10 ... optical axes T1 to T10 ... light projecting elements T15 + α, T15, T15-α ... scan period t5 ... first disturbance light detection period (inspection period)
t6, t9 ... Projection stop period (disturbance light discrimination time)
t7: First disturbance light determination period t8: Second disturbance light detection period (inspection period)
t11 ... Second disturbance light determination period U ... Projection interval (projection cycle)

Claims (7)

A projector having a plurality of projector elements;
A light projection control means for repeating a light projection scanning operation for sequentially emitting the plurality of light projecting elements at a predetermined light projection period at a predetermined scan period;
A light receiver having a plurality of light receiving elements arranged so as to constitute an optical axis facing the plurality of light projecting elements, respectively;
When any one of the plurality of light projecting elements emits light, the optical axis is shielded by detecting a light reception signal from the light receiving element for the light receiving element that forms a pair with the light projecting element. A shading determination means for performing the determination;
When any one of the plurality of light projecting elements emits light, the light receiving element that forms a pair with the light receiving element constitutes at least one of the light projecting elements immediately before and immediately after the light emitting period. In the inspection period, disturbance light detection means for detecting the presence or absence of disturbance light for each optical axis based on detecting a light reception signal from the light receiving element,
On the condition that the disturbance light is detected by the disturbance light detection means, the light projecting element does not emit light on the optical axis next to the optical axis where the disturbance light is detected and faces the light projecting element. The light receiving element performs light receiving retry operation for receiving light again in the light receiving element on the optical axis where the disturbance light is detected without receiving light, and the disturbance light is detected during the inspection period during the light receiving retry operation. Disturbance light type determination means for determining the type of disturbance light based on whether a light reception signal is detected for the light receiving element constituting the optical axis,
When the received light signal is detected by the disturbance light type determination unit, the next scan cycle is changed. When the received light signal is not detected by the disturbance light type determination unit, the next scan cycle is not changed. Adjusting means;
A multi-optical axis photoelectric sensor.   The disturbance light type determination means is a light in which the disturbance light is detected at least in the first light reception retry operation when performing the light reception retry operation on the optical axis where the disturbance light is detected by the disturbance light detection means. The multi-optical axis photoelectric sensor according to claim 1, wherein the light receiving element facing the light projecting element performs a light receiving operation without emitting light from the light projecting element on the shaft.   The disturbance light detecting means detects the presence or absence of disturbance light for each optical axis based on detecting a light reception signal from the light receiving element in a period immediately before and after a light emission period of the light projecting element, When the disturbance light detection means detects the disturbance light in a period immediately before the light emission period of the light projecting element, and when the disturbance light detection means detects the disturbance light in a period immediately after the light emission period of the light projection element. 3. The multi-optical axis photoelectric sensor according to claim 1, wherein the period adjusting unit changes the scan period to a different period.   When the disturbance light detection means detects the disturbance light immediately before the light emission period of the light projecting element, the period adjustment means shortens the scan period, and the disturbance light detection means emits the disturbance light. The multi-optical axis photoelectric sensor according to any one of claims 1 to 3, wherein the cycle adjusting means lengthens the scan cycle when detected immediately after the light emission period of the optical element.   5. The multi-optical axis photoelectric sensor according to claim 1, further comprising: a light-reception retry operation limiting unit that performs the light-reception retry operation for a predetermined number of retryable times.   The multi-optical axis photoelectric sensor according to claim 5, wherein the number of retries is the total number of retry operations for all optical axes.   If the disturbance light is detected by the disturbance light determining means when the number of times of the light reception retry operation reaches the number of retryable times and the last light reception retry operation is performed, the abnormality that has detected the disturbance light is detected. The multi-optical axis photoelectric sensor according to any one of claims 1 to 6, further comprising an abnormality detection signal output means for outputting an abnormality detection signal for informing that a state is present.

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